Conservation of Energy

Question 1

A 3 kg object is raised vertically by 4 m. Taking g = 10 m s⁻², its increase in gravitational potential energy is:

• A30 J
• B70 J
• C120 J
• D240 J

Question 2

Two objects of masses m and 3m are raised through heights 3h and h respectively. Assuming the same gravitational field strength, the ratio of their gains in gravitational potential energy is:

• A1:1
• B1:3
• C3:1
• D9:1

Question 3

A body of weight 80 N is lifted vertically by 2.5 m at constant speed. The work done against gravity is:

• A32 J
• B200 J
• C320 J
• D800 J

Question 4

A stone falls freely from rest from a height of 20 m. At what height above the ground will its kinetic energy equal its remaining gravitational potential energy? Assume negligible air resistance.

• A5 m
• B10 m
• C15 m
• D20 m

Question 5

A ball is thrown vertically upward. Neglecting air resistance, at the highest point its:

• AKinetic and potential energies are both zero
• BKinetic energy is maximum and potential energy is minimum
• CKinetic energy is zero and gravitational potential energy is maximum
• DTotal mechanical energy is zero